Field of the Invention
The present invention relates to a light source unit having semiconductor light emitting elements and a projector having the same light source unit.
Description of the Related Art
In these days, data projectors are used on many occasions as an image projection system which projects an image of a screen and a video image of a personal computer, as well as images based on image data which is stored on a memory card or the like on to a screen. In these data projectors, light emitted from a light source is collected to a micromirror display device called a DMD (Digital micromirror Device) or a liquid crystal panel for displaying a color image on the screen.
Conventionally, the mainstream of these data projectors has been those which utilize a high-intensity discharge lamp as a light source. In recent years, however, there have been developed projectors which have a light source including a semiconductor light emitting element such as a laser diode which emits a laser beam of a high light intensity and a high luminance with consumed power.
For example, the Japanese Unexamined Patent Publication No. 2011-133782 (JP-A-2011-133782) discloses a projector having an excitation light shining device in which a plurality of blue laser diodes are arranged into a matrix configuration. A luminescent light emitting device uses light emitted from the excitation light shining device as excitation light to thereby emit luminescent light in the green wavelength range. Then, laser beams emitted from the blue laser diodes of the excitation light shining device are shone on to a shining spot on a luminescent plate with major axes of elliptic cross sections of the individual blue laser beams being caused to overlap at an angle of 45 degrees or 90 degrees.
In general, it is known that a laser beam emitted from a laser diode which is a semiconductor light emitting element is coherent light. Consequently, as in the projector of JP-A-2011-133827, in the light emitted from the excitation light shining device in which the plurality of laser diodes are arranged in to the matrix configuration, in case the laser beams emitted from the individual laser diodes overlap, a wavelength interference is generated. Then, in the event that the pencil of light in which the wavelength interference is generated is shone on to a luminescent material as excitation light, Unevenness in luminance or color is generated in projected light which is displayed on the screen through the use of the luminescent light from the luminescent material as a light source.
Additionally, in the conventional arrangement of laser diodes, adjacent laser beams which strike the surface of the luminescent material are arranged to lie with a narrow gap defined therebetween, and therefore, there exits a possibility that adjacent laser beams strike the luminescent material while overlapping each other due to unevenness in direction in which laser beams are emitted from the laser diodes or mechanical tolerance in relation to the mechanisms involved. As this occurs, there is caused a possibility that the luminescent material is saturated to thereby reduce the light emitting efficiency.